Trauma
Question 112 of 180
A 64 year old woman present to the Emergency Department complaining of fever and malaise. She has no past medical history. One week ago she was scratched on her left arm by her cat. On examination you note crusted papules at the scratch site. She is febrile with tender lymphadenopathy in the left axilla. What is the most likely causative agent?
Answer:
Cat-scratch disease, caused by Bartonella henselae, typically presents with a mild infection at the wound site 3–14 days after the injury, followed by lymphadenopathy and symptoms including fever, malaise, headache, and poor appetite. Lymph glands near the scratch become swollen, and swelling may persist for several months. Occasionally the eyes, brain, heart, and other organs can be affected.Bite Wounds
Trauma
Last Updated: 8th September 2022
A bite is an injury inflicted by the teeth of a human or animal. Bite wounds can take a number of forms including lacerations, puncture wounds, and crush or degloving injuries. The most common mammalian bites are associated with humans, dogs, and cats.
Pathophysiology
- Human bites:
- Human bites are either:
- Occlusal injuries — inflicted by actual biting, or
- Clenched-fist injuries ('fight bites') — sustained when a clenched fist hits a person's teeth, often during a fight, causing small wounds over the dorsum of the hand or metacarpophalangeal joints).
- Most human bites occur on the hand. Men are most frequently bitten on the hand, arm, and shoulder. Women are most frequently bitten on the breast, genitalia, leg, and arm.
- Human bites are either:
- Dog bites:
- Dog bites characteristically involve puncture wounds from the canine teeth which anchor the victim whilst the other teeth bite, shear, and tear the tissues, causing structural damage. Adult dogs have very powerful jaws. These can inflict high pressures which, in addition to the shearing forces delivered during a bite can cause deep, open cuts, crush wounds, devascularisation, and soft-tissue avulsion. In some cases, a body part may be torn off by a dog bite. The severity of a dog bite depends on the type and size of dog, with breeds such as Rottweilers, German Shepherds, and pit bull terriers able to cause significant damage.
- Dog bites are the most common mammalian bites treated in emergency departments. In the UK, around a quarter of a million people per year present to minor injury and emergency departments with dog bite injuries. Children are more often bitten by dogs than adults (with a peak incidence of 5–9 years of age).
- Cat bites:
- Cats have fine, sharp teeth and, despite having a weaker bite than dogs, inflict deep puncture wounds inoculated with saliva, and are capable of penetrating bone, joints, and tendons Fluids can only drain from the small skin puncture wounds, therefore infections such as abscesses and osteomyelitis are more common with cat bites.
Complications
- Bacterial infection:
- Wound infection
- Infective complications resulting from a bite wound include abscesses, tenosynovitis, septic arthritis, osteomyelitis and systemic spread (for example sepsis, meningitis, endocarditis, and organ abscesses)
- Human bites are most commonly infected by Streptococcus spp, Staphylococcus aureus, Haemophilus spp, Eikenella corrodens, Bacteroides spp and other anaerobes
- Most animal bite wound infections are polymicrobial and contain a mixture of aerobic and anaerobic organisms
- Tetanus (Clostridium tetani)
- Tetanus can occur after an animal bite or human bite, especially in puncture wounds or those containing devitalised tissue, dirt, or foreign bodies; however, tetanus after a human bite is extremely rare
- Syphilis
- Syphilis transmission via a human bite has also been reported
- Cat-scratch disease (Bartonella henselae)
- Cat-scratch disease may follow a bite or scratch from a cat or dog, and presents with a mild infection at the wound site 3–14 days after the injury, followed by lymphadenopathy and symptoms including fever, malaise, headache, and poor appetite. Lymph glands near the scratch become swollen, and swelling may persist for several months; occasionally the eyes, brain, heart, and other organs can be affected
- Wound infection
- Viral infections:
- Blood-borne viruses e.g. hepatitis B and C, HIV
- There is the possibility of viral transmission through human bite wounds, although the risk is low
- Rabies
- Rabies is an acute viral encephalomyelitis that is almost always fatal. It usually occurs after a person is bitten or scratched by an animal with rabies (most commonly a dog). The risk of contracting rabies in the UK is very low, as there is no indigenous rabies in terrestrial animals, but bats anywhere in the world can carry rabies-like viruses, therefore are considered to be a rabies risk
- Blood-borne viruses e.g. hepatitis B and C, HIV
- Structural damage:
- Scarring and disfigurement
- Traumatic amputation
- Tendon and joint capsule damage
- Fractures
- Neurological damage
- Psychological effects:
- Anxiety and depression
Wound assessment
- Document how and when the bite occurred.
- For human bites
- Who was bitten, and by whom.
- Whether the skin was broken or blood was involved.
- The nature of the bite (i.e. occlusal or clenched fist).
- For animal bites
- The type of animal (domesticated or wild) and its state of health or any unusual symptoms.
- Whether the attack was provoked.
- Mechanism of injury.
- For human bites
- Monitor vital signs if the bite is particularly traumatic, or sepsis is suspected.
- Examine the bite using gloves, bearing in mind that deep layers of tissue may move with positional changes after the bite injury, disguising the true depth of the wound. Document the following (record both positive and negative findings as there may be future litigation):
- The location of the wound. Photographs or diagrams may be useful.
- The size and depth of the injury.
- The type of wound (for example laceration, puncture, abrasion, crush, haematoma, avulsion, amputation).
- The degree of crush injury, devitalised tissue, nerve or tendon damage, and involvement of muscle, bones, joints, or blood vessels. Examine wounds overlying a joint through the full range of motion to detect retracted injuries and tendon rupture.
- Neurovascular function in the area distal to the bite — check pulses and sensation.
- The range of movement of any adjacent joints.
- Any lymphadenopathy.
- The presence of any foreign bodies (for example teeth) in the wound.
- Any signs of infection (for example redness, swelling, induration, necrotic tissue, purulent discharge, pain, localised cellulitis, lymphangitis, lymphadenopathy, or fever).
- Facial bites: perform an intraoral examination to exclude cheek lacerations with an intraoral communication.
- Although rare, suspect child maltreatment if there is a report or appearance of a human bite mark that is thought unlikely to have been caused by a young child. Also consider safeguarding issues if a vulnerable adult receives a bite injury.
- Assess the person's risk of tetanus, rabies and blood-borne virus infection.
Assessment of risk of tetanus, rabies and blood-borne virus infection
- To assess the risk of tetanus:
- Enquire about tetanus immunisation status.
- Determine whether the injury is considered to be a tetanus-prone wound, for example, there is:
- A delay in surgical intervention for more than 6 hours.
- A significant amount of devitalised tissue or puncture wound (especially if in contact with soil or manure).
- A foreign body in the wound.
- A compound fracture.
- Systemic sepsis.
- Assess whether the wound is likely to be at high risk due to extensive devitalised tissue or contamination with material likely to contain tetanus spores.
- To assess the risk of blood-borne viral infection (e.g. hepatitis B or C, or HIV):
- Assess the status of the person who has been bitten (and the biter if possible):
- Check their vaccination status for hepatitis B (and surface antibody response if applicable).
- Ask if they are known to be HIV positive, hepatitis B surface antigen (HBsAg) positive, or hepatitis C positive.
- Note that if the bite has not broken the skin there is no risk of blood-borne virus transmission.
- Offer testing for Hepatitis B, Hepatitis C, and HIV in an appropriate time frame.
- In most cases the status of the biter will not be known and it is often not practical to obtain a blood sample for testing, but if appropriate, and informed consent is given, the biter should also have their blood tested.
- Assess the status of the person who has been bitten (and the biter if possible):
- To assess the risk of rabies:
- Assess the:
- Country in which the person was bitten and the origin of the animal. The UK is considered to be a 'no risk' country, with no indigenous rabies in terrestrial animals. If the person was bitten abroad, PHE guidance on rabies risk by country (for terrestrial animals) categorises countries as no risk, low risk, or high risk.
- Site and severity of the wound — bites with broken skin, contamination of mucous membranes or skin lesions with an animal's saliva or body fluid, and proximal (head and neck) bites are considered to be high-risk.
- Circumstances of the bite — unprovoked bites are considered higher risk.
- Species of animal and its behaviour and health in the days and weeks after the biting incident — abnormal behaviour increases the risk of infection.
- Immune status of the person bitten based on history of rabies vaccination.
- A risk assessment should be performed on anyone who is at risk of rabies exposure using the PHE rabies post exposure risk assessment form and calendar.
- Assess the:
Wound management
- For initial wound management:
- If possible remove any foreign bodies (for example teeth) from the wound.
- Encourage the wound to bleed (if it has just occurred), unless it is already bleeding freely.
- Irrigate thoroughly with warm, running water.
- Consider the need for debridement (for example if the wound is dirty or there is non-viable tissue).
- Advise analgesia (paracetamol or ibuprofen) for pain relief, if required.
- Where body tissue has been torn off as a result of a bite, wrap any torn off parts (for example part of an ear) in clean tissue and store in a plastic bag surrounded by ice for transport.
- For wound closure (if appropriate):
- Types of wounds that may be considered for closure include uncomplicated wounds with no risk factors for infection (for example those presenting early which are not heavily contaminated, have been adequately irrigated and debrided, and do not involve underlying structures).
- Allow the following bite wounds to heal without formal closure:
- Bite wounds over 24 hours old.
- Infected bite wounds.
- Deep puncture wounds.
- Crush injuries.
- Heavy contamination.
- Uncertain adequacy of debridement.
- Bites to the limbs, hands and feet.
- For antibiotic prophylaxis:
- Human bites:
- Do not offer antibiotic prophylaxis to people with a human bite that has not broken the skin.
- Offer antibiotic prophylaxis to people with a human bite that has broken the skin and drawn blood.
- Consider antibiotic prophylaxis for people with a human bite that has broken the skin but not drawn blood if it:
- Involves a high-risk area such as the hands, feet, face, genitals, skin overlying cartilaginous structures, or an area of poor circulation.
- Is in a person at risk of a serious wound infection because of a comorbidity (such as diabetes, immunosuppression, asplenia, or decompensated liver disease).
- For prophylaxis of a human bite prescribe co-amoxiclav for 3 days. For adults who are allergic to penicillin, prescribe metronidazole plus doxycycline for 3 days.
- Animal bites:
- Prescribe prophylactic oral antibiotics for:
- Cat bites that have broken the skin and drawn blood.
- Dog bites or bites from other traditional pets which have broken the skin and drawn blood if it:
- has penetrated bone, joint, tendon or vascular structures, OR
- is deep, is a puncture or crush wound, or which has caused significant tissue damage, OR
- is visibly contaminated (for example, if there is dirt or a tooth in the wound).
- Consider prophylactic oral antibiotics for:
- Cat bites that have broken the skin but not drawn blood if the wound could be deep.
- Dog bites that have broken the skin and drawn blood if it:
- involves a high-risk area such as the hands, feet, face, genitals, skin overlying cartilaginous structures or an area of poor circulation OR
- is in a person at risk of a serious wound infection because of a comorbidity (such as diabetes, immunosuppression, asplenia or decompensated liver disease).
- For prophylaxis of a dog or cat bite, prescribe co-amoxiclav for 3 days. For adults who are allergic to penicillin, prescribe metronidazole plus doxycycline for 3 days.
- Prescribe prophylactic oral antibiotics for:
- Human bites:
- For wound infection
- Send a pus or deep wound swab for culture, before cleaning the wound (state on the form that the swab is from an infected bite).
- Treat empirically with oral antibiotics.
- Admit anyone who has a severe infection or who is systemically unwell as intravenous antibiotics may be required.
- For treatment of an infected human bite, prescribe co-amoxiclav for 5 days. For adults who are allergic to penicillin, prescribe metronidazole plus doxycycline for 5 days.
- For treatment of an infected dog or cat bite, prescribe co-amoxiclav for 5 days. For adults who are allergic to penicillin, prescribe metronidazole plus doxycycline for 5 days.
- For managing risk of tetanus, rabies and blood-borne virus transmission:
- Tetanus
- A reinforcing dose of tetanus vaccine and possibly further doses may be required if a person is not fully immunised. Usually, tetanus immunoglobulin (TIG) is not required if a person is fully immunised, but the need for TIG will depend on the person's immunisation status and whether the wound is high-risk.
- Rabies
- Post-exposure treatment and immunisation depend on the details of the exposure, the species of animal involved, and the person's immune status. It may include administration of rabies vaccine with or without human rabies immunoglobulin.
- Hepatitis B
- Post-exposure prophylaxis for hepatitis B may include giving one or more doses of hepatitis B vaccine with or without hepatitis B immunoglobulin depending on the level of exposure, the hepatitis B status of the biter, and the vaccination status of the person with the bite injury.
- Hepatitis C
- There is no post-exposure prophylaxis available for hepatitis C virus, but serial testing will be required after the bite incident. Only after this can the person be reassured they have not acquired hepatitis C.
- HIV
- Post-exposure prophylaxis for HIV is not usually required after a human bite because the risk of HIV transmission is very low. It may be considered in some circumstances (after seeking specialist advice) if, for example, either person is known to be HIV positive and the bite draws blood, or is deep.
- Tetanus
Adder Bites
Envenoming from snake bite is uncommon in the UK. Many exotic snakes are kept, some illegally, but the only indigenous venomous snake is the European common adder/viper (Vipera berus). Two other types of snake are found in the wild in the UK (grass snakes and smooth snakes) but these are non-venomous. Adders are grey or reddish-brown, with a dark zig-zag shaped stripe down their back. The majority of adder bites occur between April and September, with a marked peak in July-August. This pattern probably reflects the outdoor activity of people, combined with the seasonal behaviour patterns of adders.
Most adder bites occur to the hand or arm, with slightly lower numbers to the foot, and much lower numbers to other parts of the body. The bites are extremely painful, but very rarely life threatening. In around 70% of cases there is no or very little envenomation result in a negligible reaction or only local effects. The first symptoms may take from a few minutes to hours to become evident. Fatal envenoming is rare but the potential for severe envenoming must not be underestimated. It is estimated that in around one third of all adder bites, the snake does not actually inject any venom (a “dry bite”).
Clinical features:
The bite may cause local and systemic effects:
- Local effects include pain, swelling, bruising, and tender enlargement of regional lymph nodes.
- Systemic effects include early anaphylactic symptoms (transient hypotension with syncope, angioedema, urticaria, abdominal colic, diarrhoea, and vomiting), with later persistent or recurrent hypotension, ECG abnormalities, spontaneous systemic bleeding, coagulopathy, adult respiratory distress syndrome, and acute renal failure.
Management:
- Initial management is to reassure, give paracetamol to control pain, and immobilise the whole patient (especially the bitten limb with a splint or sling) during urgent transport to hospital.
- Early anaphylactic symptoms should be treated with intramuscular adrenaline/epinephrine.
- Any interference with the wound should be avoided. Tourniquets, ligatures, and compression bandages should not be used.
- In hospital, rapid clinical assessment of the degree of envenoming and resuscitation may be needed, followed by careful monitoring of the blood pressure and evolution of envenoming over at least 24 hours. The most important decision is whether antivenom should be given.
- Indications for european viper snake venom antiserum are:
- Hypotension with or without signs of shock
- Other signs of systemic envenoming, electrocardiographic abnormalities, peripheral neutrophil leucocytosis, elevated serum creatine kinase, or metabolic acidosis
- Local swelling that is either extensive (involving more than half the bitten limb within 48 hours of the bite) or rapidly spreading (beyond the wrist after bites on the hand or beyond the ankle after bites on the foot within about four hours of the bite)
- For those patients who present with clinical features of severe envenoming (e.g. shock, ECG abnormalities, or local swelling that has advanced from the foot to above the knee or from the hand to above the elbow within 2 hours of the bite), a higher initial dose of the european viper snake venom antiserum is recommended; if symptoms of systemic envenoming persist contact the National Poisons Information Service.
- Adrenaline injection must be immediately to hand for treatment of anaphylactic reactions to the european viper snake venom antiserum.
Other stings/bites:
Antivenom is available for bites by certain foreign snakes and spiders, stings by scorpions and fish. For information on identification, management, and for supply in an emergency, telephone the National Poisons Information Service. Whenever possible the TOXBASE entry should be read, and relevant information collected, before telephoning the National Poisons Information Service.
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- Biochemistry
- Blood Gases
- Haematology
| Biochemistry | Normal Value |
|---|---|
| Sodium | 135 – 145 mmol/l |
| Potassium | 3.0 – 4.5 mmol/l |
| Urea | 2.5 – 7.5 mmol/l |
| Glucose | 3.5 – 5.0 mmol/l |
| Creatinine | 35 – 135 μmol/l |
| Alanine Aminotransferase (ALT) | 5 – 35 U/l |
| Gamma-glutamyl Transferase (GGT) | < 65 U/l |
| Alkaline Phosphatase (ALP) | 30 – 135 U/l |
| Aspartate Aminotransferase (AST) | < 40 U/l |
| Total Protein | 60 – 80 g/l |
| Albumin | 35 – 50 g/l |
| Globulin | 2.4 – 3.5 g/dl |
| Amylase | < 70 U/l |
| Total Bilirubin | 3 – 17 μmol/l |
| Calcium | 2.1 – 2.5 mmol/l |
| Chloride | 95 – 105 mmol/l |
| Phosphate | 0.8 – 1.4 mmol/l |
| Haematology | Normal Value |
|---|---|
| Haemoglobin | 11.5 – 16.6 g/dl |
| White Blood Cells | 4.0 – 11.0 x 109/l |
| Platelets | 150 – 450 x 109/l |
| MCV | 80 – 96 fl |
| MCHC | 32 – 36 g/dl |
| Neutrophils | 2.0 – 7.5 x 109/l |
| Lymphocytes | 1.5 – 4.0 x 109/l |
| Monocytes | 0.3 – 1.0 x 109/l |
| Eosinophils | 0.1 – 0.5 x 109/l |
| Basophils | < 0.2 x 109/l |
| Reticulocytes | < 2% |
| Haematocrit | 0.35 – 0.49 |
| Red Cell Distribution Width | 11 – 15% |
| Blood Gases | Normal Value |
|---|---|
| pH | 7.35 – 7.45 |
| pO2 | 11 – 14 kPa |
| pCO2 | 4.5 – 6.0 kPa |
| Base Excess | -2 – +2 mmol/l |
| Bicarbonate | 24 – 30 mmol/l |
| Lactate | < 2 mmol/l |
